1. Field of the Invention
The invention relates to a fuel tank with a plug which is to be opened, in particular, during maintenance work and which, in the case of first use, is manufactured in one piece with the fuel tank or is connected in a materially integral manner to the latter and has holding means for a plugging part positively connectable to the fuel tank.
2. Description of the Related Art
Such fuel tanks are usually manufactured from shell parts welded to one another and are known from practice. Components, such as, for example, suction jet pumps or a fuel feed unit, which are to be used in the fuel tank, are mounted on the inner faces of the shell parts before these are welded together. The plug is designed as part of the wall of the fuel tank and is delimited, for example, by a peripheral groove. After welding, the components are arranged within the fuel tank. In the event of maintenance, the plug can be detached from the fuel tank. After the maintenance work has ended, the orifice formed as a result of the removal of the plug is closed by means of the plugging part delivered as an accessory together with the fuel tank. For this purpose, the fuel tank has a connection piece which is located below the orifice formed by the plug and which has a thread arranged on it. The initially completely closed configuration of the fuel tank has the advantage that an escape of fuel vapors out of the fuel tank when the latter is in its new state is kept particularly low. The relatively low emission of fuel vapors, which is unavoidable in the case of a reusable plug, therefore occurs only in the unlikely event of maintenance.
One disadvantage of the known fuel tank is that the connection piece provided for connecting to the plugging part and having the thread is a molding which is difficult to manufacture in geometric terms. The fuel tank is therefore highly cost-intensive to manufacture.
The problem on which the invention is based is to design a fuel tank of the type initially mentioned, in such a way that it can be produced particularly cost-effectively.
This problem is solved, according to the invention, in that the fuel tank is designed, in the region of the plug, for tapping a thread intended for fastening the plugging part.
By virtue of this design, the fuel tank according to the invention can be composed of geometrically simple shell parts. Since the thread for fastening the plugging part is generated during the assembly of such a fuel tank, the fuel tank according to the invention does not require a preformed thread. The fuel tank according to the invention can thereby be composed in each case of moldings of geometrically simple design. The individual moldings may, for example, in each case be produced in axial-removal injection molds. As a result, the fuel tank according to the invention can be produced particularly cost-effectively. The fuel tank according to the invention may, for example, be manufactured in one piece with the plug in the same way as the known fuel tank. Alternatively to this, the fuel tank according to the invention may also first be provided with an assembly orifice and the plug be adhesively bonded or welded to the fuel tank.
That region of the fuel tank according to the invention which is intended for tapping a thread has particularly high stability if the fuel tank has an annular bead running peripherally around the plug in the new state.
According to another advantageous development of the invention, the mounting of the plugging part is particularly simple if the thread is arranged on a nut to be screwed into the bead and intended for holding the plugging part.
According to another advantageous development of the invention, canting or tilting of the plugging part can be reliably avoided if the plugging part has a flange with a plurality of individual screws to be screwed into the fuel tank.
If, according to another advantageous development, the thread is designed to be selftapping, there is no need for a special tool in order to generate it in the fuel tank.
According to another advantageous development of the invention, an identification of the plug and of the limitation of the plug can be determined in a simple way if the plug is arranged in the bottom region of a trough-like depression.
An escape of fuel vapors out of the fuel tank according to the invention when the plug is detached and the plugging part is mounted can be kept particularly low if the trough-like depression has on its wall a sealing face intended for supporting sealing elements of the plugging part.
According to another advantageous development of the invention, damage to the bead when the plug is being detached can be reliably avoided if the bead is arranged in that region of the fuel tank which is adjacent to the trough-like depression.
The bead can easily be seen during the mounting of the plugging part if the bead is arranged on the outside of the fuel tank. This avoids the situation where the plugging part is fastened next to the bead.
According to another advantageous development of the invention, a supporting ring surrounding the bead can reliably prevent the bead from moving away laterally when the plugging part having the external thread is being screwed in.
According to another advantageous development of the invention, a release of the supporting ring and therefore of the plugging part can be reliably prevented if the supporting ring and the plugging part are connected to one another via an antiloss device. This antiloss device may be designed, for example, as a tongue arranged on one of the components and capable of being folded round against the other component.
According to another advantageous development of the invention, distortion of the sealing face in the trough-like depression when the plugging part is being fastened can be avoided in a simple way if the bead is arranged on the inside of the fuel tank and is at a slight distance from the trough-like depression. This leads, particularly when the plugging part is to be screwed to the fuel tank according to the invention via a plurality of screws, to the fuel tank according to the invention being leaktight permanently and to a high degree.